Cooling tubes for glass filament production apparatus

ABSTRACT

This invention relates to glass filament production. Conventionally the hollow cooling tubes and/or solid metal bars utilized in the making of continuous glass fibers have been constructed of high temperature corrosion resistant materials whose costs are exorbitant for extensive present day factory operations. The present invention dramatically reduces the price of cooling tubes 24 suitable for use in the making of glass filaments by coating or cladding a relatively inexpensive base or substrate metal 48 such as nickel, Inconel, molybdenum, copper, alloys thereof or a refractory material with a high temperature corrosion resistant material 50 such as the noble metals, e.g. platinum, palladium, rhodium, iridium, gold, silver or alloys thereof. Fins 52 which may be attached to the cooling tubes 24 may be made either of a solid noble metal or may also be coated or clad in the same manner as the cooling tubes 24.

TECHNICAL FIELD

This invention relates to glass handling apparatus and more particularlyto cooling tubes for use with a glass filament forming apparatus.

BACKGROUND OF PRIOR ART

In one well known method and apparatus of making fibers from a molteninorganic material, such as glass, a plurality of small orifices ororifice tips are formed in the base of a molten glass chamber orbushing. The molten material flows from the bushing out of the orificetips forming cones at the end of the tips. When the temperature of themolten material at these cones is properly controlled, continuous fibersor filaments can be drawn from the tips of the cones.

Cooling means are commonly utilized for controlling the temperature ofthe cones in order to effectively and accurately regulate the transitionof the molten glass viscosity. One prior art manner of controlling thetemperature of the cones is to place a tube adjacent to the cones and tocause a cooling medium such as water to flow through the tube at a ratenecessary to maintain a desired cone temperature. The molten glassviscosity conventionally is first maintained at a relatively low leveland a very fluid condition proximate the bottom of the chamber adjacentthe discharge orifices in order to promote an effective flow therein anda full uninterrupted discharge. Thereafter the viscosity is brought torelatively higher viscosities following discharge from the orifices togovern the attenuation of the fluid stream into a filament of aptdimensions and to increase its coherency thereby minimizing breakage.

Conventional cooling means which have heretofore been utilized proximatethe area of the fluid glass stream as it emerges from the orificesinclude either tubes carrying water or other liquid coolants and/orsolid metal bars positioned transverse to the length of the bushing. Thetubes or bars have traditionally been composed of noble or similarexotic metals or alloys thereof. These materials effectively endure thehigh temperatures and corrosive vapors encountered proximate thebushing. As is well known, the environment around the cooling tubesincluding the area around the cooling tube supports, is harsh in termsof high temperature, corrosiveness caused by the temperature, volatilesfrom the molten material and water spray typically used around thebushing. At times, depending on the material used, this harshenvironment deteriorates the cooling tubes or bars requiring one or moreto be replaced at more or less periodic time intervals.

Previously the materials used include platinum, gold, silver, palladium,and the like. However, the costs of such materials are exorbitant forextensive factory operations.

BRIEF SUMMARY OF INVENTION

It is an object of the present invention to provide an economical andeffective cooling means for use with a glass filament forming apparatus.

Another object of the instant invention is the provision of relativelyinexpensive and long lasting cooling means useful in the making ofcontinous glass filaments.

A further object of the invention is the provision of coated or cladcooling means in which a noble metal is coated on a less expensivesubstrate.

These and other objects are attained in a glass filament formingapparatus by the present invention in which cooling tubes and/or barsare provided which comprise a base metal clad with a noncorrosive metalsuch as the precious or noble metals. The base metals may be selectedfrom the group consisting essentially of nickel, Inconel, molybdenum,copper, alloys thereof or refractory metals. Additionally, the preciousmetal may be selected from the group consisting essentially of platinum,palladium, rhodium, iridium, gold, silver or alloys thereof.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a partial perspective view of a conventional fiberizingbushing utilizing an example of the cooling means of the presentinvention.

FIG. 2 is a cross-sectional view of a cooling tube constructed inaccordance with the present invention.

DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS

Referring now to FIG. 1, a conventional resistance heated fiberizingbushing 10 utilizing the cooling means of the present invention isshown. The bushing 10 is fixed on conventional bushing supports 12located at each end of the bushing and is provided with two end walls14, each containing a lug 16 for attaching electrical leads (not shown).Sidewalls 18, and a bottom wall or tip plate 20 complete theconstruction of the bushing. The tip plate 20 contains a plurality oforifices or nozzles, each of which is surrounded by a tip 22 extendingbelow the tip plate 20.

A plurality of cooling means 24 are spaced along the width of the tipplate 20 in such a manner that a cooling means 24 is juxtaposed betweentwo rows of tips with one row on each side of a cooling mean 24. In thepresent example the cooling means are shown as cooling tubes 24 althoughin practice the cooling means 24 could be constructed as solid coolingbars joined to heat sinks such as a water cooled tube (not shown) andcould be located across the bushing instead of along the bushing asshown for the cooling tube 24 in FIG. 1. The alignment and spacing ofeach cooling tube 24 with respect to the tips 22 adjacent to the coolingtube is important and is maintained with alignment members 26. Themembers 26 have slots or notches at proper intervals across their lengthinto which the cooling tubes 24 are fitted. The notches in the variousalignment members 26 are aligned ensuring that the cooling tubes 24 arelikewise aligned.

The cooling tubes 24 are held in the notches of the alignment members 26by a plurality of cooling tube supports 28 which in turn are fixed by aplurality of bolts 30, washers 32, 34 and upper and lower flange nuts 36and 38, respectively. Particularly the washer 32 is and preferably boththe washers 32 and 34 are attached to the nuts 36 and 38 in any suitablemanner, as for example by brazing, pins, etc. This prevents the washersfrom causing problems when an operator is changing the cooling tubes.

The cooling tubes 24 are maintained at the proper position below the tipplate 22 by adjusting the upper nuts 36 to the correct position andsubsequently raising the support members 28 to a snug position againstthe upper washers 32 by the use of the lower washers 34 and the lowernuts 38.

In the embodiment shown in FIG. 1, the support members 28 comprise twobars 40 and 42 held in a spaced apart position by two pins 44 and 46.For reasons of economy, conventional groove or spring pins arepreferred. The ends of these pins are smaller in diameter than thecentral portion, thus forming a shoulder that butts against the insidesurfaces of the bars 40 and 42 and maintains the desired spacing betweenthe bars. The ends of the pins 44 and 46, which have a smaller diameter,fit tightly into holes drilled into the bars 40 and 42. By selecting apin material having a higher coefficient of thermal expansion than thebars, such as stainless steel pins and molybdenum alloy bars, the fitbecomes even tighter when the support is exposed to elevated servicetemperatures.

As shown in FIG. 1, the cooling tubes 24 are usually bent downward on atleast one end to facilitate their connection to lines bringing coolingfluid, usually water, to the cooling tubes. The opposite ends of thecooling tubes are frequently open. Water flowing freely from the openends into a catch basin which readily indicates that the tubes are notplugged.

According to the present invention more practical and inexpensivecooling tubes for the foregoing application and system are produced bycoating or cladding a base metal, such as nickel, Inconel, molybdenumand copper, alloys thereof or refractory metals with a noble or preciousmetal such as platinum, palladium, rhodium, iridium, gold, silver oralloys thereof. The use of the base metals allow the reduction of theunit cost of the cooling tubes while the coatings of the noble metals onthe relatively inexpensive substrates prevents the rapid corrosion anddeterioration of the cooling tubes in the very aggresive ambientconditions of high temperature combined with the corrosive vaporsencountered proximate the glass filament bushing. The use of nickel asthe base metal is preferred because it provides a good bond with all ofthe mentioned precious metals. The selection of the precious metal isbased mainly on the relative costs of the metals which change daily onthe commodity markets. The clad cooling tubes may be made by anyconventional cladding method and have been found to performsatisfactorily in the working environment.

FIG. 2 shows a cooling tube 24 of the present invention in which asubstrate tube 48, made of one of the base metals referenced above, iscoated or clad with a precious metal 50, of the types mentioned earlier.A fin 52 may be suitably affixed to the tube 24 in order to increase thestrength and thermal performance of the tube. In the embodiment shown,the fin may be made of solid precious metal such as platinum, althoughit is possible to clad a base metal such as nickel with a precious metalsuch as platinum and then braze or otherwise suitably attach the cladfin to the clad cooling tube. While FIG. 2 indicates that the crosssection of the tube 24 is oval, the tube could be provided with anycross section including a circular cross section. Additionally and alsooptionally, the tube 24 could be provided with one or more solid or cladfins which are disposed at appropriate locations about the periphery ofthe tube.

To provide adequate physical integrity which allows the cooling tubes toendure the aggresive and rigorous conditions encountered proximate thebushing commensurate with the most effective cooling through heatexchange and removal, the thickness of the base metal in the tube wallsshould be of a thickness ranging between 0.010 to approximately 0.030inches and preferably about 0.015 to 0.025 inches thick. The thicknessof the precious metal should be of a thickness ranging between about0.004 to approximately 0.008 inches and preferably 0.005 to 0.007inches.

Cooling tubes of the construction of this invention in service with aconventional glass forming apparatus should effectively resist the harshenvironmental conditions encountered therein, in particular the veryhigh tempertures and corrosive vapors of the glass melt over a prolongedperiod of 24 months of continuous or intermittent production. Priorcooling tubes using noble or exotic type metals such asplatinum-palladium alloy tubes and platinum-rhodium tubes areprohibitively expensive, whereas the clad tubes of this invention costmuch less while performing substantially as effectively.

While only one embodiment of the invention has been shown herein it willbe evident that various changes in the construction and arrangement ofparts may be resorted to without departing from the scope of theinvention as defined by the claims.

I claim:
 1. In an apparatus for forming glass filaments comprising thecombination of: a chamber for the containment of molten glass, saidchamber having a base, a plurality of small orifices in said base fordischarging fine streams of molten glass from said chamber forattenuation into filaments; a plurality of cooling means positionedbeneath and in proximity to said base, said cooling means being arrangedto extend intermediate said orifices to cool glass filaments being drawnfrom said chamber, wherein said cooling means are each formed as ahollow tube from a base metal clad with a layer of noble metal; saidbase metal being selected from the group consisting of nickel, inconel,molybdenum, copper, alloys of these materials, and refractory metals,said hollow cooling tube having a wall thickness within the range of0.010 to 0.030 inches; said noble metal being selected from the groupconsisting of platinum, palladium, rhodium, iridium, gold, silver, andtheir alloys, said noble metal cladding layer having a secondary wallthickness within the range from about 0.004 to 0.008 inches.
 2. Theapparatus of claim 1, wherein a fin is fixedly attached to each of saidcooling tubes, the material of said fin comprising a noble metal.
 3. Theapparatus of claim 1, wherein the hollow cooling tubes have a base metalwall thickness within the range of 0.015 to 0.025 inches.
 4. Theapparatus of claim 1, wherein the thickness of said noble metal is inthe range from about 0.005 to 0.007 inches.